Caterpillars hitting many drought-stressed trees

That "rain sprinkle" sound in the woods when it isn't raining is probably caterpillar droppings

submitted by Michelle Mobly

The sound of raindrops on tree leaves and the little greenish-brown pellets on the sidewalk are related to a common summertime phenomenon – leaf-hungry caterpillars.

"Leaf-devouring insects such as variable oak leaf caterpillars are just part of the onslaught faced each summer by Arkansas' trees," said Tamara Walkingstick, associate director of the Arkansas Forest Resources Center, part of the University of Arkansas System Division of Agriculture. "The good news is that birds and other predators will take care of them and if the trees are healthy, they'll put on new foliage."

"As for the pellets, they're fecal pellets, the byproduct of all that leaf-eating," she said. "Those pellets falling on leaves are what cause that raindrop sound in the woods.

"The pellets can also stain concrete, so if you have lots of them on your sidewalk or patio or other surface, sweep them off before the rain comes or you water your grass, or you'll have smeared, hard-to-remove stains," she said.

"If you go for a walk in the woods, wear a hat," Walkingstick said with a laugh.

While Arkansas' wet spring helped return moisture to the soil, effects of previous years' drought and this summer's heat and dry weather are also prompting changes in trees.

"We need to remember is that the impact of drought is cumulative and can take several years to manifest," she said. "Trees don't really fully recover from prolonged drought."

Trees hurt by last year's drought might have smaller and fewer leaves than usual.

"This could start a downward spiral if they can't produce enough food to sustain themselves," Walkingstick said. "I have a maple whose foliage is somewhat sparse this year. It and other trees are already losing some leaves and the leaves that are there are often deformed and smaller than normal. Some are changing color."

The shedding tactic to preserve water also affects "some fruit- and nut-bearing trees that lose those fruit and nuts," she said. "Drying conditions signal the tree to drop the fruit in order to sustain itself. That's fairly normal."

Hypoxylon canker, caused by a fungus, is also seen in larger areas on trees.

"This is an impact of the past years' drought," Walkingstick said. "The canker is caused by a fungus that's always present in the soil. Stressed trees become susceptible and eventually die."

There's no cure for hypoxylon canker, but prevention, by maintaining tree health, is the best medicine, she said.

Other signs you might see on trees this summer:

"Windowpaned" leaves – These are leaves where the green parts have been eaten out, leaving a translucent white skin and veins. This is a sign oak skeletonizer larvae have been chewing on leaves. Large outbreaks or successive defoliations can lead to death in part of the tree crown.Bark stains – What looks like a black oil stain on an oak's bark can be a sign of red oak borers. Borers can degrade the wood and if there is a large enough infestation, can eventually kill a tree.For more information contact the Cleburne County Extension Office, 501-362-2524.